It is well known that acute kidney injury (AKI) has a marked impact on clinical outcomes, including short-term mortality. Futhermore, the incidence of AKI has increased over the past several years. At the same time, the prevalence of chronic kidney disease is high and results in a major burden for patients and for the health care system in the United States. It is unclear if AKI is a completely reversible disease, or whether it leads to permanent kidney damage and thus CKD and death. This proposal will utilize a prospective cohort design that will add a long-term follow-up component to an ongoing multi-center 5-day study of urinary biomarkers for the detection of AKI after cardiac surgery. We will longitudinally study the patients with AKI as defined by at least a 25% increase in peri-operative serum creatinine and an equal number of patients without AKI that survive cardiac surgery at three academic centers. We will determine if AKI results in an increase in the decline in glomerular filtration rate and in increase in the protein excretion rate over time. We will compare the incidence of doubling of serum creatinine, dialysis or death in patients with and without AKI. In addition, we will examine if newly discovered biomarkers of acute kidney injury (urinary IL-18 and NGAL) are associated with CKD and death. As troponin has shown tremendous value in the setting of myocardial infarction, our hope is that these urinary biomarkers will possess long-term prognostic value for patients with AKI. Currently, AKI is viewed by most physicians as a reversible phenomenon that has little consequence after the acute phase. If, however, AKI is truly associated with long-term morbidity and mortality, then post-AKI care of these patients should involve closer vigilance and more aggressive treatments in order to improve long-term outcomes. My hope is to obtain R01 grants in the future with the goal of improving risk- stratification of AKI and I also hope to participate in multi-center trials of therapies for AKI and its associated complications.